Are Cameron Diaz and Alex Rodriguez Kaput?

Looks like Cameron Diaz can ease up on her rigorous iron-pumping schedule. Us Weekly says the lately big-bicepped star has parted ways with Alex Rodriguez after about 18 months of super-buff togetherness.

"They broke up recently," tattles a source close to the New York Yankees slugger.

So, what went wrong?

"She's very busy with her career," explains the insider. "And he's had injuries and wants to focus on his game. They're dedicated professionals."

Of course, this isn't the first time split talk has swirled around the gym-focused flames, whose romance kicked off with a bump-and-grind session at a Miami Super Bowl bash in 2010.

Rift rumors originally surfaced in October 2010, when A-Rod, 36, allegedly kicked Cam to the curb, only to reconcile with her a short time later.

Then, in June, the actress, 39, was said to be "secretly mourning the end of the relationship," which supposedly fizzled because she "pushed for more of a commitment."

Insiders quickly denied the report, and the couple put the kibosh on split whispers by getting their PDA on in Los Angeles, New York and Miami.

Not long after, rumblings began that they were looking to shack up together in Alex's $24 million Miami mega-mansion.

While there's no official word from their reps, the spy tells Us, "They're still very friendly and like each other. He has an enormous amount of respect for her."